Ron and I agree. I was just trying to avoid some of the NEC speak that confuses
people. The point is you only want one bonding point between the neutral and
ground and if the transfer equipment doesn't switch neutral that will be the
jumper in your service panel.
(Separately derived source is NEC speak for a system where the neutral is
switched too so it will have separate bonding jumpers that go with the source).
All the frame grounding will be bonded, no matter what the transfer scheme.
Adding another electrode only insures that the ground on the case is more
closely referenced to the dirt under your feet when you are standing there.
Depending on where you live "ground shift" is more or less of a problem.
Here is the sandbox (Florida) I have seen 35 volt transients across 30-40 feet
between buildings.